The effects of commercial culture of oysters Crassostrea gigas, on submerged aquatic vegetation (SAV), Zostera manna, were examined w~t h rephcated field expenments in the South Slough estuary Oregon USA Both stake and rack methods of oyster culture resulted In signlf~cant decreases in the abundance of SAV compared to undisturbed reference areas SAV cover in both stake and rack treatments was less than 25% of that In reference plots after 1 yr of culture, and was absent from rack treatments after 17 mo of culture Field experments using marked plants revealed no difference in growth between plants in stake and reference plots Compansons of sediment surface topography demonstrated that oyster culture resulted in significantly greater sediment deposition in stake plots and greater eroslon In rack plots Silt-clay fractions and carbon content of sediments tended to increase w~t h stake culture and decrease w~t h rack culture but only for carbon content at racks were the differences significant between culture and reference plots Stake culture likely affected SAV via increased sedimentation and direct physical disturbance dunng placement and harvest, while increased eroslon and perhaps shading resulted in the marked decrease in SAV co~ncident with rack culture These results indicate the potential for significant loss of SAV from estuanne ecosystems where these methods of oyster culture and SAV coincide